Conventionally, a technique of generating drive assisting information based on intersection information of an intersection before an assisting vehicle approaches the relevant intersection, and performing driving assistance on the assisting vehicle based on such drive assisting information is known. For example, Patent Literature 1 discloses a car navigation system in which an advancing direction at a second intersection is displayed with a guiding arrow short of a first intersection in successive intersections.
Patent Literature 2 discloses a technique where when a vehicle does not stop short of a traffic signal, first signal cycle information corresponding to such case is selected to perform traveling assistance of the vehicle, and when the vehicle stops short of the traffic signal, second signal cycle information corresponding to such case is selected to perform the traveling assistance of the vehicle. In this technique, signal cycle information including all information of the first signal cycle information and all information of the second signal cycle information is generated and transmitted to the vehicle if a display time band of the signal associated with the first signal cycle information and a display time band of the signal associated with the second signal cycle information do not overlap, and signal cycle information including all information of the first signal cycle information and information excluding the information associated with the overlapping display time band from the second signal cycle information is generated and transmitted to the vehicle if the respective display time bands overlap. Patent Literature 3 discloses a technique of adding priority to guiding information, map information, and the like, and changing the guiding information, the map information, and the like in accordance with the priority so that the total amount of information falls within a memory capacity when the total amount of information up to the next communicable region including a communication inappropriate region on a guiding path of the vehicle exceeds the memory capacity.